Functional laminates are documents resulting from the lamination of a plurality of layers. In particular functional laminates are used as security documents such as smart cards, ID cards, credit cards and the like. Functional laminates also refer to semi-finished products like pre-laminates or inlays, which are used for example for the manufacturing of smart cards equipped with chips or chip modules, RFID antennae and the like. They usually consist of a number of core layers and two or more cover layers covering the core layers, wherein a chip module is embedded in the layers. The layers usually consist of a plastic material such as polycarbonate or polyethylene terephthalate.
International publication WO2009135823 to HID GLOBAL discloses an example of a functional laminate, which is able to absorb mechanical stress caused by shrinkage of the cover layer in the laminating process. When the layers are laminated using heat and/or pressure the macromolecules of the plastic material tend to shorten thus causing the plastic material to shrink. Since the chip module itself does not shrink the material is subjected to mechanical stress eventually leading to deforming, cracking or delaminating the material thus limiting the service life of the functional laminate. The functional laminate is achieved by using a patch layer placed adjacent to a support layer supporting the chip or chip module. A material from which the patch layer is made will flow around the chip or chip module during lamination, thereby creating a zone around the chip that absorbs mechanical stress when the functional laminate is subjected to heat. A similar structure with similar function is also described in International publication WO200761303 and US publication U.S. Pat. No. 4,450,024.
Another solution for protecting a chip or chip module inside a functional laminate against mechanical stress is to inject a resin material in the zone around the chip or chip module. Such solutions are described for example in German publication DE 19716912 and European publication EP 1 161 48. The latter also discloses a cavity in the support layer, in proximity of the zone where the chip or chip module is located, whereby the cavity is arranged as a reservoir to receive any excess resin during the injection process.